Apparatus and method for processing a substrate

ABSTRACT

A method of processing a substrate is disclosed. The method includes the following steps: providing a substrate body having a surface; placing a die on the surface, wherein the die acts as a catalyst; immersing the substrate body and the die in a reaction solution; and processing the substrate body via a chemical reaction occurring on the surface through the reaction solution and the catalyst.

CROSS REFERENCE

This application claims the benefit of Taiwan Patent Application No.104104167, filed on Feb. 6, 2015, at the Taiwan Intellectual PropertyOffice, the disclosures of which are incorporated herein in theirentirety by reference.

FIELD OF THE INVENTION

The present invention is related to a method of substrate processing. Inparticular, the present invention is related to a method of cutting asubstrate through chemical reactions.

BACKGROUND OF THE INVENTION

For years, the method of obtaining wafers from a silicon ingot was byusing diamond wire cutting, which is a mechanical process. Althoughequipped with nearly fully-automated production equipment, theproduction lines in the industry still inevitably generate considerablewafer material loss, and considerable amount of water, electricity andconsumables (such as diamond cutting fluids and metal cutting wires,etc.) are also required. Therefore, the wafer cutting process has becomeone of the key processes for wafer processing in pursuit of lower cost.

In addition, regarding the process of manufacturing gallium nitridelight-emitting diodes (LEDs) on a surface of a substrate, sapphire isthe most common substrate. However, the processing of sapphire isrelatively difficult and time-consuming due to the intrinsic propertiesof the material. There is a great demand of technologies which iscapable of replacing existing processes. Silicon has been extensivelyused in various semiconductor, electro-optical, photovoltaic industriesfor years. Silicon has thus emerged as one of the alternative materialsto replace sapphire substrate. In order to improve the materialproperties such as the differences in lattice constant as well as thethermal expansion coefficient between the LED materials (such as galliumnitride) and the silicon substrate, the epiaxial growth of the LEDmaterial should be thoughtfully controlled. Processing and even makingpatterns on the silicon substrate surface might offer a solution to thistechnical challenge. The lithography process with photo masks iscurrently used to create patterns on the surface of a silicon substrate.However, the facility and operational costs of the lithography processfor putting a pattern on silicon substrate surfaces are extremely high,and it makes the cost reduction of LED products difficult.

In order to overcome the drawbacks in the prior art, the presentinvention introduces a novel cost-effective method of substrateprocessing. The particular design in the present invention not onlysolves the aforementioned problems, but is also easy to implement. Thus,the present invention has utility for the industry.

SUMMARY OF THE INVENTION

A novel cost-effective method of substrate processing is disclosed. Inaccordance with one aspect of the present invention, a method ofprocessing a substrate is disclosed. The method includes the followingsteps: providing a substrate body having a surface; placing a die on thesurface, wherein the die acts as a catalyst; immersing the substratebody and the die in a reaction solution; and processing the substratebody via a chemical reaction occurring on the surface through thereaction solution and the catalyst.

In accordance with another aspect of the present invention, an apparatusfor cutting a silicon ingot is disclosed. The apparatus comprises a mainbody containing a reaction solution and the silicon ingot, wherein thesilicon ingot includes at least two adjacent cutting peripheries, andthe at least two adjacent cutting peripheries define therebetween asilicon wafer; and a cutting catalyst element disposed inside the mainbody, and contacting one of the at least two adjacent cuttingperipheries to cut the silicon ingot.

In accordance with a further aspect of the present invention, a methodof forming a pattern on a non-conductive substrate is disclosed,comprising the steps of: (a) providing a substrate body having asurface; and (b) forming the pattern on the surface via a catalyticreaction.

The objectives and advantages of the present invention will become morereadily apparent to those ordinarily skilled in the art after reviewingthe following detailed descriptions and accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-1C are schematic diagrams showing the apparatus and method forprocessing a substrate according to one embodiment of the presentinvention;

FIG. 1D is a schematic diagram showing an embodiment of slicing a waferout of a substrate or a silicon ingot;

FIG. 2 shows another embodiment of the apparatus and method forprocessing a substrate according to the present invention;

FIG. 3A shows yet another embodiment of the apparatus and method forprocessing a substrate according to the present invention;

FIG. 3B shows a further embodiment of the apparatus and method forprocessing a substrate according to the present invention;

FIG. 4 shows yet another embodiment of the apparatus and method forprocessing a substrate according to the present invention;

FIG. 5A is an SEM picture of a die which is a matrix composed ofpyramid-shaped dies;

FIG. 5B shows an SEM picture of the pattern made with the die shown inFIG. 5A; and

FIGS. 6A-6C shows curves related to the cycles of current versuspotential obtained through a cyclic voltammetry test.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described more specifically withreference to the following embodiments. It is to note that the followingdescriptions of the preferred embodiments of this invention arepresented herein for the purposes of illustration and description only;they are not intended to be exhaustive or to be limited to the preciseform disclosed.

The present invention makes use of a chemical reaction, particularlywith the aid of a catalyst, to cut an ingot to obtain wafers orsubstrates, or to form patterns on a surface of a substrate. Thematerial of the ingot or the substrate can be silicon or galliumnitride. Compared to the traditional mechanical process of ingot dicing,slicing and wafering, the present invention can increase the processingefficiency, improve the surface roughness of the substrates and reducematerial losses during the sawing process.

Please refer to FIGS. 1A-1C, which show schematic diagrams of theapparatus and method for processing a substrate according to oneembodiment of the present invention. According to FIG. 1, a main body 18contains reaction solution 12 and the substrate 10 to be cut. At least acutting catalyst element or cutting die 11 is disposed on the surface 17of the substrate 10. It can be observed that both the substrate 10 andthe die 11 are immersed in the reaction solution 12, which contains anetching solution. With the cutting die 11 acting as catalyst andcontacting the substrate 10 at the contact surface 14, an etchingprocess on the surface 17, more specifically at the contact surface 14,takes place via a chemical reaction occurring. As time goes by, thecontact surface 14 will move along the direction 15 which is downward inthe illustration of FIG. 1A due to gravity, and eventually the substrate10 will be cut through by the cutting die 11, as illustrated in FIG.1B-1C. If two cutting dies 11 are configured on the surface 17 of thesubstrate 10, at least a wafer 13 can be obtained after the cuttingprocess is completed. Notably, the substrate 10 can be a silicon ingot,so the mentioned process can be used to cut wafers out of the siliconingot. For better contact between the cutting dies 11 and the substrate10 at the contact surfaces 14, a pressure source (not shown) providingpressure upon the substrate 10 can be added to the cutting dies 11 tofacilitate the cutting process.

According to another embodiment of the present invention, the cuttingdies 11 can be disposed underneath the substrate 10 so that gravitycaused by the weight of the substrate 10 can provide pressure upon thecontact surfaces (not shown) between the cutting dies 11 and thesubstrate 10 for better contact therebetween. If necessary, a pressuresource (not shown) providing pressure can be added to the substrate 10to enhance the completion of the cutting process. In some embodiments,the cutting dies 11 can take the shape of lines.

Please refer to FIG. 1D, which is a schematic diagram showing anembodiment of slicing a wafer out of a substrate or a silicon ingot.According to FIG. 1D, the substrate 10 has at least two adjacent cuttingperipheries 16, which define therebetween a silicon wafer 13. Thecutting die 11 is disposed inside the main body 18, and contacts one ofthe at least two adjacent cutting peripheries 16 to cut the substrate10, which is a silicon ingot in one embodiment. Repeating this process,a silicon ingot can be sliced into wafers piece by piece. This mannercan obtain wafers from an ingot without sacrificing much material duringthe cutting process, because the cutting catalyst element can be formedas a very thin wire which is much thinner than traditional diamond saws.

Please again refer to FIGS. 1A-1C. The method of cutting a substrate 10according to the present invention includes the following steps: (1)cleaning the surface of the substrate 10; (2) mixing hydrofluoric acid(acting as an etching solution) with hydrogen peroxide (acting as anoxidant) in an appropriate ratio to form the reaction solution 12. Ifnecessary, further additives, such as coordination agent, capping agent,ligands, protective agents, etching accelerator (e.g., glycine, lysine,copper sulfate, copper nitrate, copper chloride and the like), or otheroxidants (e.g., ozone) can be included; (3) adjusting and maintainingthe reaction solution 12 under weak acidic conditions; (4) using acutting die 11 such as a metal wire (a silver wire is employed in thepresent embodiment, while platinum, copper, iridium, palladium, gold,stainless steel wires and a combination thereof, or even a metal wireplated with silver, platinum, copper, iridium, palladium, gold orstainless steel can be also applicable) with a diameter of 0.5millimeter as a catalyst; (5) immersing the cutting die 11 and thesubstrate 10 into the reaction solution 12 and causing the cutting die11 to contact a surface 17 of the substrate 10 to process the substratebody via a chemical reaction occurring on the surface 17. Meanwhile, toimprove the cutting conditions and cutting quality, the proposed methodmay also include steps of measuring the etching depth on the substratebody to calculate the etching speed and measuring the roughness of thecutting surface.

In an exemplary embodiment, the material of the cutting die 11 can besilver or any other catalytic metal, the reaction solution 12 can be amixture of hydrogen peroxide and hydrofluoric acid, and the substrate 10is a silicon ingot. The chemical reactions are represented by thefollowing formulae:

-   Formula (1): the chemical reaction mechanism with silver as the    catalyst:

-   Formula (2): the chemical reaction mechanism for etching with    hydrofluoric acid:    SiO₂+6HF    H₂SiF₆+2H₂O-   Formula (3): the overall reaction formula:    Si+2H₂O₂+6HF    H₂SiF₆+4H₂O

Notably, other metals such as platinum, copper, iridium, palladium,gold, stainless steel or a combination thereof are also applicable toact as the catalyst, and the etching solution may also include sulfuricacid, hydrochloric acid, nitric acid or a combination thereof. Based onthe same concept, substrates made of sapphire, silicon carbide, galliumnitride or other non-conductive materials can be processed according tothe present invention.

Please refer to FIG. 2, which shows another embodiment of the apparatusand method for processing a substrate according to the presentinvention. In FIG. 2, the apparatus 28 is a processing apparatus forforming a pattern on the surface 27 of the silicon wafer 20. When thecutting dies 21, which are one-dimensional objects such as metal wires,are disposed on the silicon wafer 20 and contact the silicon wafer 20 atthe surface 27, the silicon wafer 20 will be cut because of the samechemical reaction as set forth above. After the silicon wafer 20 isetched to a certain depth D2, the cutting dies 21 are removed andtrenches 26 are formed on the silicon wafer 20. When the cutting die 21is a two-dimensional object such as a grid-like die, the methodaccording to the embodiment as illustrated in FIG. 2 results in agrid-like pattern on the surface 27 of silicon wafer 20. The processcharacterized by the creation of surface features on the surface 27where the surface features are reversely identical to the originalfeature on the cutting die 21.

Please refer to FIG. 3A, which shows another embodiment of the apparatusand method for processing a substrate according to the presentinvention. In FIG. 3, the apparatus 38 is a processing apparatus forforming a pattern on the surface 37 of the silicon wafer 30. When thehollow die 31, which is a three-dimensional object such as a hollow die,is disposed on the silicon wafer 30 and contacts the silicon wafer 30 atthe surface 37, the silicon wafer 30 will be cut through the samechemical reaction as set forth above. After the silicon wafer 30 isetched to a certain depth D3, the hollow die 31 is removed away and athree-dimensional pattern is formed on the silicon wafer 30. If acutting die having a rough surface pattern is employed in the cuttingprocess, the corresponding rough surface pattern can be formed on thesilicon wafer 30.

In addition, referring to FIG. 3B, a counter electrode 33 can bedisposed in opposite to the hollow die 31 in the reaction solution 12,and an electric power supply 34 is added on the circuit 35 connecting tothe hollow die 31 and the counter electrode 33 to provide an electricpower thereto to either accelerate the chemical reaction or prevent thehollow die 31 from corrosion. The electric power supply (not shown) caneither provide a constant voltage or a constant current to the system.In one embodiment, the hollow die 31 may act as an anode while thecounter electrode 33 acts as a cathode and the electric power canaccelerate the etching process to the silicon wafer 30. In anotherembodiment, the hollow die 31 may act as a cathode anode while thecounter electrode 33 an anode, the electric power can prevent the hollowdie 31 from corrosion due to the theory of cathode protection, andtherefore the catalyst service life of the hollow die 31 can beextended.

Referring again to FIG. 3B, pressure can be applied to the contact areasbetween the hollow die 31 and the silicon wafer 30 by disposing a weight36 on top of the hollow die 31 for better contact conditions between thehollow die 31 and the silicon wafer 30 to ensure the etching quality.

Likewise, similar to the prior-described embodiment, the silicon wafer30 can be alternatively disposed on top of the hollow die 31, so thatgravity due to the weight of the silicon wafer 30 provides pressure tothe contact surfaces between the hollow die 31 and silicon wafer 30 forbetter contact therebetween. If necessary, the weight 36 or another typeof pressure source can also be disposed on top of the silicon wafer 30in this configuration.

Table 1 shows the formulae of the reaction solution 12 versus results.As illustrated in Table 1, the silicon ingot can be smoothly slicedunder proper etching conditions with an appropriate oxidant. As theconcentration of hydrogen peroxide rises, the dissolution rate of thesilver wire decreases, and thus the consumption of silver is reduced.

TABLE 1 Hydrofluoric acid Hydrogen peroxide Silver dissolution (Volume(Volume rate (Milligram/ Formula Percentage) Percentage) cm²/hour) 1 5%20% Nearly 223 2 5% 10% Nearly 289 3 5%  5% Nearly 447

Please refer to FIG. 4, which shows yet another embodiment of theapparatus and method for processing a substrate according to the presentinvention. This embodiment uses a pyramid-shaped die 41 in the reactionsolution 12, and etches the wafer 40 through the pressure due to gravityfrom the weight 46 disposed on top of the pyramid-shaped die 41 whichresults in a pattern with a counter-pyramid shape on the wafer 40.

FIG. 5A shows a picture of the die which is a matrix composed ofpyramid-shaped dies as shown in the embodiment of FIG. 4. The picture istaken by a scanning electron microscope (SEM). FIG. 5B shows the SEMpicture of the pattern made with the die as shown in FIG. 5A.

According to one embodiment, sulfuric acid can be use to replacehydrofluoric acid as the etching solution. In this embodiment, sulfuricacid in various concentrations (0.5 M, 1M and 2M) is utilized, a silverwire is used as the working electrode, and a graphite rod is employed asthe counter electrode. Via an electrochemical cyclic voltammetry (CV)test, curves in cycles of current versus potential (corresponding to thecounter electrode) when the reduction and oxidation reactions occur areas shown in FIGS. 6A-6C. Based on the high symmetry of the oxidation andreduction peaks of the curves to determine the reversibility of thechemical reaction, the illustrations help the skilled person in the artto understand the electrochemical characteristics of the reactive liquidused in the embodiments, whereby it can be used to design or improve theformulation of the reaction fluid and the accelerating or inhibitingprocess.

In addition, neither the photo-lithography technique nor a photomask isrequired to implement the present invention. Therefore, the presentinvention reduces the investment cost for production facilities.Furthermore, the methods according to the present invention can beadopted to generate one-dimensional, two-dimensional orthree-dimensional patterns on a substrate with ease.

Embodiments

-   1. A method of processing a substrate, comprising steps of: (a)    providing a substrate body having a surface; (b) placing a die on    the surface, wherein the die acts as a catalyst; (c) immersing the    substrate body and the die in a reaction solution; and (d)    processing the substrate body via a chemical reaction occurring on    the surface through the reaction solution and the catalyst.-   2. The method of Embodiment 1, further comprising steps of disposing    a counter electrode in opposite to the die in the reaction solution;    and providing an electric power to the die and the counter    electrode.-   3. The method of Embodiment 2, further comprising a step of when the    die acts as an anode, applying one of a constant voltage and a    constant current to the die to accelerate the chemical reaction.-   4. The method of Embodiment 2, further comprising a step of when the    die acts as a cathode, applying one of a constant voltage and a    constant current to the die to prevent the die from corrosion.-   5. The method of the previous embodiments, wherein the reaction    solution includes an etching solution being one selected from a    group consisting of a hydrofluoric acid, a sulfuric acid, a    hydrochloric acid, a nitric acid and a combination thereof.-   6. The method of the previous embodiments, wherein the reaction    solution includes an oxidant being one of a hydrogen peroxide and an    ozone.-   7. The method of the previous embodiments, wherein the reaction    solution includes an etching additives being one selected from a    group consisting of a glycine, a lysine, a copper sulfate, a copper    nitrate, a copper chloride and a combination thereof.-   8. The method of the previous embodiments, wherein the die is one    object selected from the group consisting of one-dimensional,    two-dimensional and three-dimensional objects.-   9. The method of the previous embodiments, wherein the die has a    surface being a metal selected from a group consisting of a silver,    a platinum, a copper, an iridium, a palladium, a gold, a stainless    steel and a combination thereof.-   10. The method of the previous embodiments, wherein the substrate    body includes a material being one selected from a group consisting    of a silicon, a sapphire, a silicon carbide and a gallium nitride.-   11. The method of the previous embodiments, wherein the processing    step includes one of the following steps: forming a pattern on the    surface of the substrate body; and performing a cutting to the    substrate body.-   12. An apparatus for cutting a silicon ingot, comprising a main body    and a cutting catalyst element. The main body contains a reaction    solution and the silicon ingot, wherein the silicon ingot includes    at least two adjacent cutting peripheries, and the at least two    adjacent cutting peripheries define therebetween a silicon wafer.    The cutting catalyst element is disposed inside the main body, and    contacts one of the at least two adjacent cutting peripheries to cut    the silicon ingot.-   13. The apparatus of Embodiment 12, wherein the cutting catalyst    element includes a metal wire acting as a catalyst and being one    selected from a group consisting of a silver, a platinum, a copper,    an iridium, a palladium, a gold, a stainless steel and a combination    thereof.-   14. The apparatus of Embodiment 12, wherein the reaction solution    includes an etching solution being one selected from a group    consisting of a hydrofluoric acid, a sulfuric acid, a hydrochloric    acid, a nitric acid and a combination thereof.-   15. The apparatus of Embodiment 12, wherein the reaction solution    includes an oxidant being one of a hydrogen peroxide and an ozone.-   16. The apparatus of Embodiment 13, further comprising a pressure    source providing a pressure against the silicon ingot; and an    etching solution cutting the silicon ingot by using the metal wire.-   17. The apparatus according to claim 12, further comprising a    counter electrode in opposite to the cutting catalyst element and    disposed inside the main body.-   18. A method of forming a pattern on a non-conductive substrate,    comprising steps of: (a) providing a substrate body having a    surface; and (b) forming the pattern on the surface via a catalytic    reaction.-   19. The method of Embodiment 18, further comprising a step of    providing an etching solution and a metal die, wherein the catalytic    reaction occurs at a contact surface where the metal die contacts    the surface of the body, the substrate body acts as a reactant, the    metal die acts as a catalyst; and when the contact surface proceeds    with the catalytic reaction, the pattern is formed on the contact    surface.-   20. The method of Embodiment 19, further comprising steps of    disposing a counter electrode in opposite to the metal die in the    etching solution; and providing an electric power to the metal die    and the counter electrode.

While the invention has been described in terms of what is presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the invention needs not be limited to the disclosedembodiments. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims, which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures.

What is claimed is:
 1. A method of processing a substrate, comprisingsteps of: providing a substrate body having a surface; placing a die onthe surface, wherein the die acts as a catalyst; immersing the substratebody and the die in a reaction solution; and processing the substratebody via a chemical reaction occurring on the surface through thereaction solution and the catalyst, wherein the reaction solutionincludes an etching accelerator being one selected from a groupconsisting of a glycine, a lysine, a copper sulfate, a copper nitrate, acopper chloride and a combination thereof.
 2. The method according toclaim 1, further comprising steps of: disposing a counter electrode inopposite to the die in the reaction solution; and providing an electricpower to the die and the counter electrode.
 3. The method according toclaim 2, further comprising a step of: when the die acts as an anode,applying one of a constant voltage and a constant current to the die toaccelerate the chemical reaction.
 4. The method according to claim 2,further comprising a step of: when the die acts as a cathode, applyingone of a constant voltage and a constant current to the die to preventthe die from corrosion.
 5. The method according to claim 1, wherein thereaction solution includes an etching solution being one selected from agroup consisting of a hydrofluoric acid, a sulfuric acid, a hydrochloricacid, a nitric acid and a combination thereof.
 6. The method accordingto claim 1, wherein the reaction solution includes an oxidant being oneof a hydrogen peroxide and an ozone.
 7. The method according to claim 1,wherein the die is one object selected from the group consisting ofone-dimensional, two-dimensional and three-dimensional objects.
 8. Themethod according to claim 1, wherein the die has a surface being a metalselected from a group consisting of a silver, a platinum, a copper, aniridium, a palladium, a gold, a stainless steel and a combinationthereof.
 9. The method according to claim 1, wherein the substrate bodyincludes a material being one selected from a group consisting of asilicon, a sapphire, a silicon carbide and a gallium nitride.
 10. Themethod according to claim 1, wherein the processing step includes one ofthe following steps: forming a pattern on the surface of the substratebody; and performing a cutting to the substrate body.
 11. A method offorming a pattern on a non-conductive substrate, comprising steps of:providing a substrate body having a surface; and forming the pattern onthe surface via a catalytic reaction, wherein the reaction solutionincludes an etching accelerator being one selected from a groupconsisting of a glycine, a lysine, a copper sulfate, a copper nitrate, acopper chloride and a combination thereof.
 12. The method according toclaim 11, further comprising a step of providing an etching solution anda metal die, wherein: the catalytic reaction occurs at a contact surfacewhere the metal die contacts the surface of the body; the substrate bodyacts as a reactant; the metal die acts as a catalyst; and when thecontact surface proceeds with the catalytic reaction, the pattern isformed on the contact surface.
 13. The method according to claim 12,further comprising steps of: disposing a counter electrode opposite tothe metal die in the etching solution; and providing an electric powerto the metal die and the counter electrode.